Jonathan Clarke, who will have to resit English GCSE, is fronting the campaignTimes photographer, Mary Turner

A legal challenge is to be started today seeking to force exam boards to issue new grades to tens of thousands of teenagers who sat English GCSEs this summer.

The challenge, led by Lewisham Council, southeast London, is seeking a judicial review of the decisions by two exam boards, AQA and Edexcel, to move grade boundaries by large margins for candidates who sat the same exams in January and June.

It also attempts to challenge the role of Ofqual, the independent exams regulator, which has admitted that grades awarded for GCSE English in January were too lenient but refused to sanction new grades for candidates who sat the exam in June.

Lewisham, a Labour authority, is bringing the action on behalf of 163 teenagers who…